Although the physiological effects of continuous noise on cochlear function are well documented in the literature, the effects arising from impact noise exposure have not yet been characterized. This is a direct consequence of the difficulty in generating and calibrating impact noise under laboratory conditions. A prototype impact noise generator has been used to test the widely accepted hypothesis that different types of noise of equal energy produce similar damage in the cochlea. Our results indicate that during 20 mins exposure and 1 hour recovery the suppression of responses produced by impact or continuous noise of equal energy are markedly different. The study of whether this difference persists after longer exposure and recovery periods awaits the development of a more durable noise generator which is presently under way.